ZIROX SGM5T User manual

ZIROX Sensoren & Elektronik GmbH
Am Koppelberg 21,17489 Greifswald, Germany [phone], Fax: -29, e-mail: [email protected]
ZIROX Oxygen Measuring Technology
SGM5T
Oxygen monitor
for inert and reactive gases
Manual

Oxygen monitor SGM5T Content
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Table of contents
1 General information ...................................................................................................... 4
1.1 Introduction.......................................................................................................... 4
1.2 Copyright ............................................................................................................. 4
1.3 Commonly used symbols..................................................................................... 5
2 Application fields........................................................................................................... 6
3 Safety regulations ......................................................................................................... 7
4 Functional description .................................................................................................. 8
4.1 Measuring principle.............................................................................................. 8
4.2 General recommendations................................................................................... 9
4.3 Gas flow rate ..................................................................................................... 10
4.4 Accuracy of the measurement ........................................................................... 10
5 Technical data ............................................................................................................. 12
5.1 Characteristics................................................................................................... 12
5.2 Mechanical data / ambient conditions ................................................................ 12
5.3 Electrical data.................................................................................................... 12
5.4 Interface data..................................................................................................... 13
6 Composition of the oxygen monitor SGM5T ............................................................. 17
6.1 General composition.......................................................................................... 17
6.1.1 General overview ................................................................................... 17
6.1.2 Construction principle of the solid electrolyte sensor .............................. 18
6.1.3 Electronic data processing ..................................................................... 19
6.2 Composition of the oxygen monitor SGM5T....................................................... 20
6.2.1 The mechanical composition .................................................................. 20
6.2.2 Current supply........................................................................................ 20
6.2.3 Front ...................................................................................................... 20
6.2.4 Rear ....................................................................................................... 21
7 Installation and initiation ............................................................................................ 22
7.1 Installation conditions ........................................................................................ 22
7.2 Set-up of operating state ................................................................................... 22
8 Operation and parametrization................................................................................... 24
8.1 Operation........................................................................................................... 24
8.1.1 Switch-on and measurement indication.................................................. 24
8.1.2 Gas flow ................................................................................................. 24
8.1.3 Data monitoring...................................................................................... 24
8.1.4 Status and error messages .................................................................... 25
8.2 Parametrization ................................................................................................. 26
8.2.1 Adjustable parameters ........................................................................... 26
8.2.2 Programming menus.............................................................................. 27
8.3 Calibration ......................................................................................................... 29

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8.3.1 Zero calibration ...................................................................................... 29
8.3.2 Span gas calibration............................................................................... 29
8.4 Fault clearance.................................................................................................. 30
9 Maintenance, overhaul and storage........................................................................... 31
9.1 General notes.................................................................................................... 31
9.2 Replacement of the equipment fuse .................................................................. 31
10 Appendix...................................................................................................................... 32
10.1 Fundamentals of the use of potentiometric ZrO2solid electrolyte sensors for the
optimal running of combustion processes ................................................................... 32
10.2 Mounting instructions for Swagelok®-fittings .................................................. 37
10.3 Activated carbon filter: description and application notes................................ 38
10.3.1 Filter construction................................................................................. 38
10.3.2 Application and operation of the filter.................................................... 38
10.3.3 Replacing ............................................................................................. 38
10.3.4 Technical data...................................................................................... 39
10.4 Declaration of conformity ................................................................................ 40
10.5 Warranty conditions........................................................................................ 41
11 Your own notes and remarks...................................................................................... 42

Oxygen monitor SGM5T 1 General information
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1 General information
1.1 Introduction
This manual describes composition, mode of operation and use of
the oxygen monitor SGM5T of the ZIROX Sensoren und Elektronik
GmbH.
Address of manufacturer:
ZIROX Sensoren & Elektronik GmbH
Am Koppelberg 21
17489 Greifswald
GERMANY
Tel.: [phone]
Fax: [phone]
E-mail: [e-mail]
The manufacturer guarantees that this manual was written in accordance with
the functional and technical features of the delivered SGM5T.
This manual is not subject to the amendment service. If the manufacturer
modifies the SGM5T with the aim of making technical improvements, the user
is responsible for inserting the additional or updated pages supplied.
Proper operation of the SGM5T can only be ensured if the contents of this
manual are known. Therefore, all chapters of this manual must be read
carefully prior to operating the SGM5T.
The values on the device display in this manual are examples or preset
parameters of the manufacturer. Process-specific parameters must be set by
the user.
Pages, charts and figures are numbered consecutively.
1.2 Copyright
This operation manual is copyright protected.
It must not be partially or completely reproduced, copied, or distributed, without
prior written permission of the manufacturer. The use for competitive
advantages or the distribution to third parties are not authorized either.
All rights reserved.

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1.3 Commonly used symbols
Symbol for imminent danger:
This symbol refers to imminent danger to persons’ life and health.
In case of disregard fatal injuries may result.
Symbol for indirect danger:
This symbol indicates indirect danger.
The degree of the damage depends on the circumstances and the actions of
the persons involved.
In case of disregard destruction or damage of the SGM5T, its single
components or other material assets as well as minor injuries may result.
Symbol for proper handling:
This symbol appears where the manual refers to the adherence to rules,
instructions and proper operation.
In case of disregard damage or destruction of the SGM5T or its single
components may result.
attention
danger
danger

Oxygen monitor SGM5T 2 Application fields
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2 Application fields
The protective gas monitor SGM5T serves the continuous measuring of the
oxygen concentration in industrial, laboratory and protective gases as well as
in the process of mixing and producing of special forming gases in industry.
The measuring of the free oxygen concentration in inert gases and also the
measuring of bound oxygen in gas mixtures is possible.
The main application areas of the oxygen monitor are the following:
• food processing industry, in particular the production processes in
breweries and food packing;
• processes of mixing and producing forming gases;
• production processes of welding and soldering, especially gas-shielded
arc welding in steel and container production as well as plant
construction
• production processes of electronic components under buffer gas.
The introduction of explosive gas compounds, high concentrations of
halogens and sulphuric gases (e.g. SO2) into the SGM5T is not permitted.
The contact of the SGM5T with siliconic or phosphoric compounds is not
permitted either.
The SGM5T Functions
• measures and indicates the oxygen concentration in a measuring gas
continuously;
• indicates any deviations of the oxygen concentration in the measuring
gas from an adjustable set value;
• monitors the course of a particular production process under buffer gas;
• checks the purity of buffer gases and determines whether the requested
protective effect of the buffer gas is reached.
The requirements and limit values provided in "Technical data" must be strictly
observed.
Any other use is treated as non-authorized use.

Oxygen monitor SGM5T 3 Safety regulations
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3 Safety regulations
The following regulations for industrial safety provide basic information about
potential danger during the operation of the buffer gas monitor SGM5T.
Therefore, they must be observed and strictly followed by the responsible staff.
• A failure-free and functional operating of the SGM5T can only be
guaranteed with knowledge of this manual. Therefore, all chapters of this
manual must be read carefully before the installation and initiation of the
SGM5T.
• The SGM5T is to be used for the functional operation only (see chapter
2).
• The SGM5T is to be installed, operated, and serviced by trained staff
only.
• The SGM5T is to be connected to an isolated ground socket (Schuko-
socket) with the supplied cable.
Explosive gas mixtures, halogens in high concentration, and sulphuric gases
(e.g. SO2) are not permitted to be measured by this SGM5T.
Because of the high operation temperature of the sensor, the SGM5T
produces a lot of heat. Make sure the device does not overheat because of
covering.
A vertical installation may cause heat accumulation and damage to the device.
Switch off and disconnect the device from the power supply before opening
the housing cover.
Special safety instructions for potential danger during certain working
processes are provided in relevant text passages.

Oxygen Monitor SGM5T 4 Functional description
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4 Functional description
4.1 Measuring principle
In industry and laboratories the measurement of the oxygen concentration in
gases is often required. Mostly, it is measured in gases which have a
considerable, temperature-independent oxygen concentration.
The NERNST equation is used as a basis for determining the oxygen
concentration in gases with the oxygen monitor SGM5T.
NERNST
equation
U
RT
F
p
p
O air
O meas gas
=4
2
2
ln ,
, .
(I)
U – cell voltage in V
R – molar gas constant, R = 8.314 J/ (mol · K)
T – measuring temperature in K
F– Faraday-constant, F = 9.648 · 104C/mol
pO2,air – partial pressure of the oxygen at the reference electrode in dry
air in Pa
pO2,meas.gas – partial pressure of the oxygen at the measuring electrode in
the measuring gas in Pa.
The sensor of the SGM5T is based on the conductivity of oxide ions in a
special ceramic substance (zirconium dioxide) with stabilizing additions. The
conductivity of these oxide ions increases exponentially with the temperature
and reaches a sufficiently high temperature above 600°C.
The gas to be measured passes through the ceramic oxide ion conductor
which is a gas-tight tube. The ceramic tube is situated axially symmetrically in
a thermally well-insulated heater. The electrodes of the galvanic sensor are
made from platinum. The electrode on the outside of the tube, surrounded by
dry air, is used as a reference electrode with a constant, known electrode
potential (composition see chapter 6.1.2).

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Based on the assumption that the total pressures of the gases are almost the
same at both electrodes (in this case the volume concentrations may be used
in the calculation instead of the partial pressures) and replacing the
parameters by numbers in equation (I) the following equation applies:
Equation
for oxygen
concentration
ϕ
O2=20.64 · e (-46.42 · U
T
)(II)
ϕ
O2 – oxygen concentration in the measured gas in vol%
U – potential difference in mV
T – measuring temperature in K
20.64 – oxygen concentration in air with a relative humidity of 50% in vol%.
4.2 General recommendations
The oxygen may be in free or bound form inside the measuring gas1. (see
chapter 10.1)
Thereby, the following dependencies are valid:
– for free oxygen
– for bound oxygen
The equation (II) for calculating the oxygen concentration is valid for
measuring gases with free oxygen as well as for reducing gas mixtures in
which oxygen only exists in bound form (e.g. in H2/H2O- or CO/CO2-mixtures).
In reducing gas compounds, the oxygen partial pressure is inversely
proportional to the temperature. For converting the measured value at the
measuring temperature into other temperatures special thermodynamic
equations are required.
Reducing gas
compounds
1Different conditions of oxygen in the measuring gas must be distinguished:
Free oxygen: Oxygen molecules in the gas are independent without a bond to other gas components (inert gases
such as N2or Ar).
Bound oxygen: Free oxygen molecules do not exist in the gas, only in bound form e.g. as water vapor. Higher
temperatures cause a dissociation and oxygen molecules are available. Since the dissociation degree increases
with the temperature, the measurement result depends on the temperature.
Possibly, free oxygen can react with potential burnable gases at the hot platinum electrode. The result can be a
reducing gas.
U T~
U
T
~1

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When intentionally producing and monitoring reducing exhaust gases from the
reaction of fuel with air, the air factor λcan be calculated and displayed if the
chemical compounds and their concentration in the fuel are known.
For λ< 1 the calculation and indication of the CO-, CO2-, H2- and H2O-
concentrations is possible. For this, special counseling from the manufacturer
is required.
Air factor λ
4.3 Gas flow rate
For exact measurements a flow rate between 5 and 10 l/h of the measuring
gases must be ensured (see also chap. 8.1.2).
Contamination effects of the gas tubes (leaks, permeability, desorption) may
cause falsified measuring result if the flow rate is too low.
Asymmetric cooling of the sensor electrodes may cause falsified
measuring results if the flow rate is too high. In extreme case (pressure
surge or gas flow > 20 l/h), damage to the sensor is possible.
The gas flow rate is measured by a pressure difference sensor. The SGM5T
displays an error message when the limit values are over- or underrun.
However, the measuring will be continued.
If the device is operated with an internal pump, the gas flow will be regulated
by the pump. An optimum gas flow of 8l/h is set.
4.4 Accuracy of the measurement
The manufacturer guarantees a measuring error of less than 3% (relative
error) only with measurements of oxygen concentrations within a range of 2 ·
105 ... 10 ppm. For measurements of oxygen concentrations of 10 ... 10-3 ppm
the relative error is less than 5% if the gas inlet tube has no leaks or
permeability.
For measurements of oxygen concentrations less than 10 ppm, the following
aspects must be taken into account during evaluation:
• composition of the measuring gas (e.g. presence of burning gases)
• specific characteristics of the production process (e.g. material used)
• temperature of the measuring gas.
To reduce the measuring error in low oxygen concentrations, the following
conditions must be provided:
• The measuring gas must be extracted where a formation of layers can
be avoided.
• The tube from the measuring point to the SGM5T must be as short as
possible in order to avoid a change in the chemical balance in the tube.
• All gas inlet and outlet tubes must be free of leaks.
• For measurements of oxygen concentrations of less than 1000 ppm, the
use of steel tubes is necessary.
NOTE
NOTE